schmidt flow sensor instructions for use · symbols used in this manual ... figure 3-2 arrangement...

SCHMIDT® Flow Sensor

SS 20.600

Instructions for Use

Instructions for Use SS 20.600 Seite 2

SCHMIDT® Flow Sensor

SS 20.600

Table of Contents

1 Important information....................................................................... 3

2 Application range ............................................................................. 4

3 Mounting instructions....................................................................... 7

4 Electrical connection...................................................................... 20

5 Signaling ........................................................................................ 25

6 Commissioning .............................................................................. 30

7 Information concerning operation .................................................. 31

8 Service information ........................................................................ 32

9 Dimensions .................................................................................... 36

10 Technical data ............................................................................... 37

11 Declaration of Conformity .............................................................. 39

Imprint:

Copyright 2016 SCHMIDT Technology

All rights reserved

Ausgabe: 535084.02B

Subject to modifications


1 Important information

The instructions for use contain all required information for a fast com-missioning and a safe operation of SCHMIDT

® flow sensors.

These instructions for use must be read completely and observed carefully, before putting the unit into operation.

Any claims under the manufacturer's liability for damage resulting from non-observance or non-compliance with these instructions will become void.

Tampering with the device in any way whatsoever - with the excep-tion of the designated use and the operations described in these in-structions for use - will forfeit any warranty and exclude any liability.

The unit is designed exclusively for the use described below (refer to chapter 2). In particular, it is not designed for direct or indirect pro-tection of personal or machinery.

SCHMIDT Technology cannot give any warranty as to its suitability for a certain purpose and cannot be held liable for errors contained in these instructions for use or for accidental or sequential damage in connection with the delivery, performance or use of this unit.

Symbols used in this manual

The symbols used in this manual are explained in the following section.

Danger warnings and safety instructions. Read carefully!

Non-observance of these instructions may lead to injury of per-sonal or malfunction of the device.

General note

All dimensions are given in mm.

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2 Application range

The SCHMIDT® flow sensor SS 20.600 is designed for stationary

measurement of the flow velocity as well as the temperature of pure1 air

and gas with operating temperature up to 120 °C and working pressure up to 40 bar.

The sensor is based on the measuring principle of a thermal anemome-ter and measures the mass flow of the measuring medium as flow veloci-ty which is output in a linear way as standard velocity

2 wN (unit: m/s),

based on standard conditions of 1013.25 hPa and 20 °C. Thus, the re-sulting output signal is independent of the pressure and temperature of the medium to be measured.

When using the sensor outdoors, it must be protected against direct exposure to the weather.

If the sensor head is immersed in water and operated under pressure, the sensor may be damaged irreversibly.

Using the sensor in flammable gases the regulations of ATEX guidelines has to be applied (see below).

The sensor variants for use in potentially explosive atmosphere (ATEX) and oxygen (O2) are not combinable.

ATEX

The ATEX version of the sensor is designed for use in explosive gas at-mosphere of zone 2 (corresponding to EPL Gc). ATEX-specific infor-mation can be found in the additional ATEX instructions.

The additional ATEX instructions (535698.02) must be read and observed carefully when using the sensors in ATEX areas.

The operation in continuously or frequently occurring explosive atmosphere is not allowed.

1 No chemically aggressive contents /abrasive particles; check suitability in individual cases

2 Corresponds to the actual velocity under standard conditions

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Grease-free and O2

In version “grease-free and for O2 > 21 %”, the sensor, the accessories and the packaging have been cleaned especially according to the stand-ard IEC/TR 60877:1999.

This standard may be restricted by:

- The operating specification of the SS 20.600 with regard to temper-ature and pressure.

- Special conditions regarding the use of diatomic oxygen (O2).

The use of the oxygen version is limited to:

- Maximum pressure of the medium of 20 bar. - Maximum temperature of the medium of 60 ° C.

Exceeding these limits can lead to danger to persons and mate-rial.

The improper use of gas mixtures having an oxygen percentage of at least 21% or pure oxygen can cause fire or explosion.

It is explicitly pointed out that the customer, when opening the packaging, assumes full responsibility for the cleanliness of the sensor and its accessories according to the standard IEC/TR 60877:1999.

Information concerning the compliant handling of O2

The general rule is that a soiling of sensor parts that come into contact with oxygen must be absolutely avoided:

- The installation site must be carefully cleaned before mounting the sensor.

- Make sure to use only clean tools and material for the installation.

- Before opening the packaging film, remove the dirt such as dust from the film, if necessary.

- If possible, open the packaging film and take out the sensor directly at the installation site.

- Otherwise open the packaging film at an appropriate and clean workplace and store the sensor in an appropriate, cleaned, dust- and humidity-tight container.

- Do not touch the oxygen contacting sensor parts with bare hands.

- Use clean and non-fluffy gloves or cloths or similar to handle the sensor.

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Special gases

The “gas” version of the SS 20.600 is equipped with a correction for the measurement of certain gases and gas mixtures. The sensor is adjusted and calibrated in air. Then a special correction for the medium to be measured is applied to the sensor. The correction has been determined for many gases in real gas ducts. For gas mixtures, the correction is cal-culated according to the set volumic mixing ratio.

Mechanical versions

The sensor SS 20.600 is available in a version as compact sensor and as a remote sensor. The dimensions can be found in the dimensional drawings in chapter 9.

The customer is responsible for the observance of all relevant statutory provisions, standards and directives relating to the use of gases.

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3 Mounting instructions

General information on handling

The flow sensor SS 20.600 is a precision instrument with high measuring sensitivity. In spite of the robust construction of the sensor head, soiling of the inner sensor elements can lead to distortion of measurement re-sults (see also chapter 8). During procedures like transport, mounting or dismounting of the sensor that facilitates soiling, it is generally necessary to attach the enclosed protective cap of SCHMIDT Technology to the sensor head and remove it only during operation.

During processes with risk of soiling such as transport or mounting, the protective cap should be placed on the sensor head.

Mounting method

The SS 20.600 can be mounted only by means of a through-bolt joint which supports the sensor tube and ensures positive clamping. The through bolt joint as well as a pressure protection kit is included in the scope of delivery. Due to the variety of applications the through bolt joint exhibits different versions which share the following features:

Pressure range: 40 bar (overpressure)

Media temperature: min. -20 … +120 °C

Material: Screw-joint components made of stainless steel 1.4571

Clamping ring made of VA steel

Variations are made on the one hand by the design of the external screw thread (order option: G½ or R½), on the other hand by the materials and properties of the used O-seals:

Standard: NBR (operating parameters see above)

Oxygen (O2): FKM (BAM approval)

ATEX: FKM (suitable from -40 °C)

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Systems with overpressure

Depending on the version, the SS 20.600 is designed for a maximum working pressure of 16 bar (standard) or 40 bar (option). As long as the medium to be measured is operated with overpressure, make sure that:

There is no overpressure in the system during mounting.

Mounting and dismounting of the sensor can be carried out only as long as the system is in a depressurized state.

Only suitable pressure-tight mounting accessories are used.

Appropriate safety devices are installed to avoid unintended discard-ing of the sensor due to overpressure.

For measurements in media with overpressure, appropriate safety measures must be taken to prevent unintended dis-carding of the sensor.

If other accessories than the delivered pressure protection kit or alterna-tive mounting solutions are used, the customer must ensure the corre-sponding safety measures.

The pressure-tight mounting, the fastening of the screw pipe connection and the discarding protection must be checked be-fore pressure is applied. These tightness checks must be re-peated at reasonable intervals.

The components of the pressure protection kit (bolt, chain and bracket) have to be checked regularly for integrity.

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Thermal boundary conditions

With medium temperatures exceeding or underrunning the permitted ambient temperatures of the electronics, a cooling or heating section of the sensor tube of at least 50 mm must be provided (see Figure 3-1) to prevent that the electronic components located in the electronic housing are influenced by the medium temperature.

Figure 3-1

Make sure that the transmission of the medium temperature does not cause the temperature of the electronics to exceed or underrun the permitted operating temperature range.

Flow characteristics

Local turbulences of the medium can cause distortion of measurement results. Therefore, appropriate mounting conditions must be guaranteed to ensure that the gas flow is supplied to the sensor in a laminar

3, i.e.

quiet and low in turbulence, state. The corresponding measures depend on the system properties (pipe, chamber, etc.) which are described in the following subchapters for different mounting variants.

Correct measurements require a (laminar) flow low in turbu-lence.

3 The term “laminar” means here an air flow low in turbulence (not according to its physical definition saying that the Reynolds number is < 2300).

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General installation conditions

The sensor head of SS 20.600 consists of two basic elements:

The enclosing measuring chamber:

The measuring chamber, also referred to as chamber head, protects the inner sensor chip from mechanical and electrical influences.

The aerodynamically optimized design allows tilting around the longi-tudinal axis of the sensor up to ±3° relative to the ideal measuring di-rection (see Figure 3-2) without significant impact on the measure-ment result

4.

The axial tilting of the sensor head relative to the flow di-rection should not exceed ±3°.

The center of the chamber head also used for specification of probe length (L) is the actual measuring point of the flow measurement and must be placed in the flow as advantageous as possible, for example in the middle of the pipe.

Position the sensor head always at the most advantageous position for flow measurement.

The sensor chip:

The measurement direction is clearly defined by the measuring prin-ciple (unidirectional).

The measuring direction is indicated by means of two arrows; the first indication is located on the front of the chamber head, the other one printed on the housing cover below the LED indication (see Fig-ure 3-2). With the remote version, an additional arrow is located at the cable end of the sensor.

Note:

If the sensor has been mounted in the wrong direction (rotated by 180° relative to the flow direction) and flow is available, it does not output zero but wrong (too high) measuring values.

The sensor measures unidirectional and must be adjusted correctly relative to the flow direction.

4 Deviation < 1 % of the measured value

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Figure 3-2 Arrangement of flow direction arrows

The design of the sensor element results in a minimal coupling between heater and medium temperature sensor, leading to a thermal crosstalk at minimal flow velocity near zero that defines the lower limit of the measur-ing range.

Due to system characteristics the lower measuring range limit of the sensor is 0.2 m/s.

Under unfavorable installation conditions, convection increases thermal crosstalk.

Measurements in a downward flow (downdraft flow, see Figure 3-3) lead to considerably in-creased measuring values in the lower flow range. The area concerned depends on the sys-tem pressure. Correct measuring values are displayed above

5 2 m/s.

Figure 3-3

Avoid installation in a pipe or chamber with downward flow be-cause the lower measuring range limit can rise significantly.

5 In case of a vertical downdraft flow and a overpressure of 16 bar.

5

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±3°


Mounting in pipes with circular cross-section

Typical applications for this type are compressed air networks or burner gas supply lines. They are characterized by long thin pipes with a quasi-parabolic flow profile.

The easiest method to achieve a low-turbulence flow is to provide a suf-ficiently long and absolutely straight distance without disturbances (such as edges, seams, bends etc.) in front (inlet) and behind the sensor (out-let) (see installation drawing Figure 3-4). It is also necessary to pay at-tention to the design of the outlet distance because the flow is also influ-enced by disturbances generating turbulences against the flow direction.

Figure 3-4

L1 Length of the inlet distance

L2 Length of the outlet distance

D Inner diameter of the measuring section

The absolute length of the corresponding distances is defined by the in-ner diameter of the pipe because the flow abatement depends directly on the aspect ratio of measuring distance and diameter. Therefore, the re-quired abatement distances are specified as a multiple of the pipe diam-eter D. Besides, the degree of turbulence generation by the correspond-ing disturbing object plays an important role. A slightly curved bend di-rects the air with a relative low-disturbance level, whereas a valve gen-erates massive turbulences with its abrupt change of the flow-guiding cross-section that require a relatively long distance for abatement.

The required abatement section (based on the inner pipe diameter D) in case of different fault causes is shown in Table 1.


Flow obstacle upstream of measuring dis-tance

Minimum

length inlet (L1)

Minimum length outlet

(L2)

Light bend (< 90°)

10 x D 5 x D

Reduction, expansion, 90° bend or T-junction

15 x D 5 x D

Two 90° bends in one plane (2-dimensional)

20 x D 5 x D

Two 90° bends (3-dimensional change in direction)

35 x D 5 x D

Shut-off valve

45 x D 5 x D

Table 1 Inlet and outlet distance

This table lists the minimum values required in each case. If it is not pos-sible to observe the specified abatement distances, increased deviations of the measurement results are to be expected or it is necessary to take additional measures, for example to use flow rectifiers

6. The profile fac-

tors specified in Table 2 may become void by the use of flow rectifiers.

6 For example, honeycombs made of plastic or ceramics.


Calculation of volume flow

A quasi-parabolic speed profile is formed over the pipe cross-section under laminar conditions, whereas the flow velocity at the pipe walls re-mains almost zero, in the middle of the pipe it reaches the optimum measuring point, its maximum wN. This measured variable can be con-verted to an average flow velocity

Nw that is constant over the pipe

cross-section by means of the correction factor which is called profile factor PF. The profile factor depends on the pipe diameter

7 and is shown

in Table 2.

PF

Tube Ø Volume flow [m3/h]

Inner Outer Min. @ @ Sensor measuring range

[mm] [mm] 0.2 m/s 10 m/s 20 m/s 60 m/s 90 m/s 140 m/s 220 m/s

0.796 26.0 31.2 0.3 15.2 30.4 91.3 136.9 213.0 334.7

0.748 39.3 44.5 0.7 32.7 65.3 196.0 294.0 457.3 718.6

0.772 51.2 57.0 1.1 57.2 114.4 343.3 515.0 801.1 1258

0.786 70.3 76.1 2.2 109.8 219.7 659.0 988.5 1537 2416

0.797 82.5 88.9 3.1 153.4 306.8 920.3 1380 2147 3374

0.804 100.8 108.0 4.6 231.0 462.0 1385 2078 3233 5081

0.812 125.0 133.0 7.2 358.7 717.5 2152 3228 5022 7892

0.817 150.0 159.0 10.4 519.8 1039 3118 4677 7276 11434

0.829 206.5 219.1 20.0 999.5 1999 5997 8995 13993 21989

0.835 260.4 273.0 32.0 1600 3201 9605 14408 22412 35219

0.84 309.7 323.9 45.6 2278 4556 13668 20502 31892 50116

0.841 339.6 345.6 54.8 2742 5484 16454 24681 38393 60331

0.845 388.8 406.4 72.2 3611 7223 21669 32504 50562 79455

0.847 437.0 457.0 91.5 4573 9146 27440 41160 64027 100614

0.85 486.0 508.0 113.5 5676 11353 34059 51088 79471 124883

0.852 534.0 559.0 137.4 6869 13738 41216 61824 96170 151125

0.854 585.0 610.0 165.3 8263 16526 49580 74371 115688 181796

0.86 800.0 311.2 15562 31124 93373 140059 217870 342368

0.864 1000.0 488.6 24429 48858 146574 219861 342006 537438

0.872 1500.0 1109 55474 110948 332845 499268 776639 1220433

0.877 2000.0 1983 99186 198372 595118 892677 1388609 2182100

Table 2 Profile factors and volume flows

7 Both inner air friction and sensor locking are responsible.


Thus, it is possible to calculate the standard volume flow of the medium using the measured standard flow velocity in a pipe with known inner diameter:

AwV

wPFw

DA

NN

NN

2

4

D Inner diameter of the pipe [m]

A Cross-section area of the pipe [m2]

Nw Flow velocity in the middle of the pipe [m/s]

Nw Average flow velocity in the pipe [m/s]

PF Profile factor (for pipes with a circular cross-section)

NV Standard volume flow [m3/s]

For calculating the flow velocity or volume flow in pipes for the different sensor types, SCHMIDT Technology offers a flow calculator that can be downloaded from its homepage:

www.schmidt-sensors.com or www.schmidttechnology.com

Installation in systems with square cross-section

For most applications, there is a distinction between two borderline cas-es as regards the flow conditions:

Quasi-uniform flow field

The lateral dimensions of the flow-guiding system are approximately as large as its length in the flow direction and the flow velocity is small so that a stable trapezoidal

8 speed profile of the flow is

formed. The width of the flow gradient zone at the wall is negligible in relation to the chamber width so that a constant flow velocity can be expected over the whole chamber cross-section (the profile fac-tor is in this case 1). The sensor must be mounted here in such a way that its sensor head is far enough from the wall and it measures in the area with the constant flow field.

Typical applications are:

o Exhaust ventilation shafts for drying processes

o Chimneys

8 A uniform flow field prevails in the largest part of the space cross-section.

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Quasi-parabolic flow profile

The system length is large compared to the cross-section surface and the flow velocity is so high that the ratios correspond to that of the circular pipe. This means that the same requirements apply here to the installation conditions.

Since the situation is similar to that in a pipe9, the volume flow in a

square chamber can be calculated by equating the hydraulic diame-ter of both cross-section forms. The result for a rectangle according to Figure 3-5 is a hydraulic “pipe diameter” DR:

bK: Width of rectangular channel

hK: Height of rectangular channel

DR: Equivalent pipe diameter

kk

kkR

hb

hbD

2

Figure 3-5

According to this, the volume flow in a chamber is calculated:

N

KK

KKRNN

NN

KK

KK

KK

KKRR

whb

hbPFAwV

wPFw

hb

hb

hb

hbDA

2

22

2 2

44

bK/hK Width/height of the square chamber [m]

DR Hydraulic inner diameter of the chamber [m]

AR Cross-section area of the equivalent pipe [m2]

Nw Maximum flow velocity in the middle of the pipe [m/s]

Nw Average flow velocity in the pipe [m/s]

PF Pipe profile factor

NV Standard volume flow [m3/s]

Typical applications are:

o Ventilation shaft

o Exhaust air duct

9 The profile factors are equal for both cross-section forms.


Mounting with a through-bolt joint

The through-bolt joint is mounted using a G½ or R½ external thread. Typically, a bushing is welded as a fitting onto a bore in the medium-guiding system wall. In most applications, these are pipes which are tak-en as an example for the description of the mounting procedure below (see Figure 3-6).

Figure 3-6

L Sensor length [mm] DA Outer diameter of the pipe [mm]

SL Length of the weld-in sleeve [mm]

E Sensor tube setting length [mm]

AL Projecting length [mm] R Reference length [mm]

Installation process:

Depressurize the system for measurements with overpres-sure media and mount the pressure protection kit.

Drill a mounting bore in a pipe wall.

Weld the pipe union with an internal thread G½ or R½ in the center above the mounting opening on the pipe. Recommended length of the pipe union: 15 ... 40 mm

Plug the holding bracket of the pressure protection chain into the thread of the through-bolt joint.

Screw the threaded part of the through-bolt joint tightly into the pipe union (hexagon AF27).

Observe the correct seat and alignment of the chain bracket.

Check if there is an O-ring seal available and if it is fitted tightly.

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Loosen the spigot nut of the through-bolt joint so that the sensor probe can be inserted without jamming.

Remove the protective cap from the sensor head; carefully insert the sensor into the guide of the through-bolt joint so that the center of the chamber head is placed at the measuring position in the middle of the pipe.

Adjust the sensor manually at the sensor housing by turning it coun-terclockwise by approx. 80° (observe the flow arrow on the housing cover). Make sure that the immersion depth is maintained.

Tighten the spigot nut slightly by means of a key wrench (AF24) to fasten the sensor.

Use a fork wrench (AF27) to lock the hexagon bolt at the screw pipe connection. Use another key wrench (AF24) to tighten the spigot nut of the through-bolt joint until the arrow on the sensor housing com-plies with the direction of the pipe flow.

Check the set angular position carefully, for example by placing a bubble level on the aligning surface of the sensor housing.

The angular deviation should not be greater than 3° rela-tive to the ideal measuring direction. Otherwise, the meas-urement accuracy may be affected.

In case of wrong adjustment, the through-bolt joint has to be loos-ened and the alignment procedure must be repeated.

Shorten the safety chain by removing the superfluous chain links so that the chain is slightly tensioned after being locked at the housing. Finally, secure the chain with a padlock.

General note:

Do not use the aligning surface of the housing for mechanical alignment, such as locking. There is risk of damage to the sen-sor.

Mounting of the remote version

The sensor probe of the remote version is mounted with a through-bolt joint in the same way as the compact sensor. A wall mounting bracket is provided for fastening the sensor housing.

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Accessories

The accessories required for mounting and operation of the SCHMIDT®

flow sensor SS 20.600 are listed in Table 3 below.

Type / Article No.

Drawing Assembly

Connecting cable Standard with fixed length:

5 m 524921

- Threaded ring, knurl - Plug injection-moulded - Material:

Brass, nickel-plated PUR, PVC

Connecting cable Standard with optional length:

x m 524942

- Threaded ring, knurl - Material:

Brass, nickel-plated Polyamide, PUR, PP Halogen-free

10

Coupler socket With thread locking

524929

- Threaded ring, knurl - Material:

Brass, nickel-plated Polyamide, PUR, PP - Connection of wires: Screwed (0.25 mm

2)

Clamp11

a.) 524916 b.) 524882

- Internal thread G½, R½ - Material:

a.) Steel, black b.) Stainless steel 1.4571

Table 3 Accessories

Informations about further accessories for mounting and display can be found on our homepage:

www.schmidt-sensors.com or www.schmidttechnology.com

10

According to IEC 60754 11

According to EN 10241; must be welded.

L=5m

14

,5

5,1

42

L=XXm

20

54

5,9

54

20 für Kabel- 6-8 mm

26

,6

34

Rp

1/2

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4 Electrical connection

Make sure that no operating voltage is active during electrical installation and that the operating voltage cannot be switched on inadvertently.

The sensor is equipped with a plug-in connector which is firmly integrat-ed in the housing. The connector has the following data:

Number of connection pins: 8 (plus shield connection at the metallic housing) Type: Male Fixation of connecting cable: M12 thread (spigot nut at the cable) Type of protection: IP67 (with screwed cable) Model: Binder, series 763 Pin numbering:

View of plug-in connector of the sensor

Figure 4-1

The pin assignment of the plug-in connector can be seen from the follow-ing Table 4.

Pin Designation Function Wire color

1 Pulse 1 Output signal Flow (digital: Impulse) White

2 UB Operating voltage: 24 VDC ± 20% Brown

3 Analog TM Output signal Temperature of medium (analog: U / I) Green

4 Analog wN Output signal Flow (analog: U / I) Yellow

5 AGND Reference potential for analog outputs Gray

6 Pulse 2 Galvanically decoupled pulse output (relay) Pink

7 GND Operating voltage: Ground Blue

8 Pulse 2 Galvanically decoupled pulse output (relay) Red

Shield Electromechanical shielding Meshwork

Table 4

The analog signals have an own AGND reference potential.

The specified wire colors are valid when one of the SCHMIDT® connect-

ing cables is used (see subchapter “Accessories”, Table 3).

The appropriate protection class III (SELV) respective PELV has to be considered.

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Operating voltage

For operation in accordance with its designated use, the sensor requires a DC voltage with a nominal value of 24 VDC at an allowed tolerance of ± 20 %.

Deviating values can lead to measurement errors or even defects and, therefore, should be avoided.

Operate the sensor only within the defined voltage range (24 VDC ± 20 %).

Undervoltage may result in malfunction; overvoltage may lead to irreversible damage.

The operating current of the sensor (including analog signal currents, without pulse outputs) is normally approx. 80 mA. With pulse output

12,

the required current value increases to max. 200 mA13

.

The specifications for the operating voltage are valid for the connection to the sensor. Voltage drops generated due to line resistances must be taken into account by the customer.

Wiring of analog outputs

Both analog outputs for flow and temperature are designed as high-side driver with “Auto-U/I” feature and have a permanent short circuit protec-tion against both rails of the operating voltage.

Use of only one analog output

It is recommended to connect the same resistance value to both analog outputs, even if only one of them is used. For example, if only the “flow” analog output is operated as current output with a re-sistance value of a few ohms, it is recommended to connect the oth-er analog output (“temperature”) with the same resistance value or directly to AGND.

Nominal operation

The measuring resistance RL must be connected between the corre-sponding signal output and the electronic reference potential of the sensor (see Figure 4-2). Normally, AGND must be selected as measuring reference potential for the signal output. The supply line GND can also be used as reference potential, however, the ground offset can cause significant measurement errors in the “Voltage” op-erating mode.

12

Without signal current of the semiconductor relay. 13

Both signal outputs with 22 mA (maximum measurement values); supply voltage minimal

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Typically, AGND has to be selected as measuring refer-ence potential for the signal output.

Figure 4-2

Depending on the value of resistance RL, the signal electronics

switches automatically between the operation as voltage interface (mode: U) and current interface (mode: I), hence the designation “Auto-U/I”. The switching threshold is in range between 500 and 550 Ω (for details refer to chapter 5). However, a low resistance val-ue in voltage mode may cause significant voltage losses via the line resistances RW,S, which can lead to measuring errors.

For voltage mode, a measuring resistance of at least 10 kΩ is recommended.

The maximum load capacitance CL is 10 nF.

Short circuit mode

In case of a short circuit against the positive rail of the supply voltage (+UB), the signal output is switched off.

In case of a short circuit against the negative rail (GND) of the oper-ating voltage, the output switches to the current mode (RL is calcu-lated to 0) and provides the required signal current.

If the signal output is connected to +UB via a resistance, the value RL is calculated incorrectly and false signal values are caused.

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Wiring of the pulse output (Highside driver)

The pulse output is current-limited, short-circuit protected and has the following technical characteristics:

Design: Highside driver, open collector Minimum high level US,H,min: UB – 3 V (with maximum switching current) Maximum low level US,L,max: 0 V Short circuit current limitation: Approx. 100 mA Maximum leakage current IOff,max: 10 µA Minimum load resistance RL,min: Depending on the switching voltage UB (see below) Maximum load capacitance CL: 10 nF Maximum cable length: 100 m Wiring:

Figure 4-3

The pulse output can be used as follows:

Direct driving of low-impedance loads (e.g. optocoupler, relays, etc.) with a maximum current consumption of approx. 100 mA.

This allows calculating the minimum permitted (static) load re-sistance RL,min depending on the operating voltage UB

14:

A

VUR B

L1.0

3min,

Example:

In case of the maximum permissible operating voltage of UB,max = 28.8 V the minimal load is RL,min = 258 Ω.

Here the excessive heating power of the load has to be considered.

The pulse output is protected by means of different mechanisms:

Current limiter:

The current is limited to approx. 100 mA.

If the resistance values are too low, the length of the interconnection phases is limited to 100 µs.

The maximum load capacitance CL is 10 nF. A higher capacitance reduces the limit of the current limiter.

14

Overcurrent peaks are absorbed by the short circuit limiter.


In case of a high capacitive load CL, the inrush current im-pulse may trigger the quick-reacting short-circuit protection (permanently) although the static current requirement is be-low the maximum current IS,max. An additional resistor con-nected in series to CL can eliminate the problem.

Protection against overvoltage.

The pulse output is protected against short-term overvoltage peaks (e.g. due to ESD or burst) of both polarities by means of a TVS di-ode

15. Long-term overvoltage destroys the electronics.

Overvoltage can destroy the pulse output.

Wiring of the relay

The output is realized by a semiconductor relay and has the following technical characteristics:

Type: SSR (PhotoMOS relay) Maximum leakage current IOff,max: 2 µA

Maximum resistance RON: 16 Ω (typ. 8 ) Maximum switching current IS: 50 mA Maximum switching voltage US: 30 VDC / 21 VAC,eff Wiring:

Figure 4-4

The relay output is protected against short-term overvoltage peaks (e.g. due to ESD or burst) of both polarities by means of a TVS diode. Long-term overvoltage destroys the electronics.

The specified electrical operating values may not be exceed-ed. Exceeding the operating values may lead to irreversible damage. Protective measures for incorrect wiring are not taken for this output.

15

Transient Voltage Suppressor Diode, breakdown voltage approx. 30 V, pulse capacity 4 kW (8 / 20 µs)


5 Signaling

LEDs

The SCHMIDT® flow sensor SS 20.600 has four tricolor LEDs

16 (see

Figure 5-1) that are either indicating the flow velocity during error-free operation in a quantitative way or signal the cause of the problem (see Table 5).

Figure 5-1

No. State LED 1 LED 2 LED 3 LED 4

1 Ready for operation & flow < 5 %

2 Flow > 5 %

3 Flow > 20 %

4 Flow > 50 %

5 Flow > 80 %

6 Flow > 100 % = overflow

7 Sensor element defective

8 Operating voltage too low

9 Operating voltage too high

10 Electronic temperature too low

11 Electronic temperature too high

12 Medium temperature too low

13 Medium temperature too high

Table 5

LED off LED on: orange

LED on: green LED flashes17

: red

16

Component with two integrated LEDs (red and green) that can be controlled individually and indicate a mixed color orange together.

17 Approx. 1 Hz

LED 1


Analog outputs

Switching characteristic Auto-U/I

Resistance value interval RL Signaling mode Signaling range

≤ 500 (550) Current (I) 4 ... 20 mA

> 500 (550) Voltage (U) 0 ... 10 V

Table 6

A hysteresis of approx. 50 Ω ensures a stable transition behavior which is shown in Figure 5-2 below.

Figure 5-2

Depending on the provided output signal characteristic the accuracy of the switching point detection can be reduced. Therefore, it is rec-ommended to select the resistance such that a safe detection can be maintained (< 300 Ω for current mode and > 1 kΩ for voltage mode).

To detect possible alternating load in an actual zero signal, the elec-tronics generates test pulses that correspond to an effective value of approx. 1 mV. However, the latest measuring devices may trigger in response to such a pulse in DC voltage measuring mode and display short-term measuring values of up to 20 mV. In this case, it is rec-ommended to install an RC filter at the measuring input with a time constant of 20 … 100 ms.

Error signaling

In current mode, the interface outputs 2 mA18

.

In voltage mode, the output switches to 0 V.

18

In accordance with the Namur specification.

0 500 550

Mode

I

U


Representation of the measuring range

The measuring range of the corresponding measuring value is mapped in a linear way to the mode-specific signaling range of the associated analog output.

For flow measurement, the measuring range ranges from zero flow to the selectable end of the measuring range wN,max (see Table 7).

Voltage mode (U) Current mode (I)

wNOut

N

N UV

ww ,

max,

10

)4(16

,

max,mAI

mA

ww wNOut

N

N

Table 7 Representation specification for flow measurement

The measuring range of the medium temperature starts at the se-lected measuring range start TMin and ends at 120 °C (see Table 8).

Voltage mode (U) Current mode (I)

MinTMOutMin

M TUV

TT

,

10

120 MinTMOut

MinM TmAI

mA

TT

)4(

16

120,

Table 8 Representation specification for measurement of medium temperature

110 wN [%]0

20 40 8060 100

IOut

[mA]

20

4

21,6

12

8

16

U Out [V]

T M [°C]

10

4

2

11

120

6

8

TMin

I Out [mA]

0 TMin T M [°C]

20

4

8

22

120

12 12

16

2

U Out [V]

0 110 w N

[%]

10

0 20

11

40 80 60 100

4

2

6

8


Exceeding measuring range of flow wN

Measuring values larger than wN,max are output in a linear way up to 110 % of the signaling range (this corresponds to 11 V resp. 21.6 mA max., see graphics in Table 7). At higher values of wN, the output signal remains constant.

Error signaling does not take place because damage of the sensor is unlikely.

Medium temperature TM outside specification range

Operation beyond the specified limits can lead to damage to the sensor and, therefore, is seen as a critical error. This leads to the fol-lowing reaction depending on the temperature limit (also refer to the graphics in Table 8):

o Medium temperature below the lower temperature limit

The analog output for TM switches to error (0 V or 2 mA)19

. The measuring function for the flow velocity is switched off its analog output also signals an error (0 V resp. 2 mA).

o Medium temperature above 120 °C

TM is output in a linear way up to at least 130 °C, for example to enable overshooting of heating control. The flow velocity is measured and displayed further on.

Above this critical limit, flow measurement is switched off and the analog output wN switches to error signaling (0 V or 2 mA). The signal output TM switches directly to the maximum values of 11 V resp. 22 mA, as opposed to the normal error signaling.

In case of excessive temperature, this avoids harmful coupling of the heating control that might be measuring by means of the medium temperature sensor. The standard error signaling of 0 V (possibly also 2 mA) could be identified by the control as a very low temperature of the medium which would lead to further heat-ing.

19

The switching hysteresis for the threshold is approx. 5 K.


Pulse outputs

The pulse outputs as opposed to the analog outputs represent the flow velocity wN.

The standard version maps the flow velocity wN proportional to a selectable frequency range from 0 to fmax (see Figure 5-3).

Figure 5-3 Example for fmax = 100 Hz

Hzf 100...10max

max,

max

Nw

f

f

Nw

max,

max

NV

f

f

NV

NV : Standard volume

flow

The volume flow and the pulse valence VN,Imp (= volume per pulse) can be determined on base of the output frequency, the measuring range of the sensor and the pipe diameter D.

2

4

DPFNwDAPFNwNV

;

max

max,

Imp, f

NV

NV

The version configured according to the requirements of the cus-tomer supplies pulses with predefined pulse valency (e.g. 1 m³/pulse).

To do this, the pipe diameter must be specified when ordering.

Exceeding the measuring range of the flow wN is also output up to 110 % of the measuring range. The output of higher flow values is limited to 110 % of the measuring range.

If an error occurs, 0 Hz or no pulses will be output. The current initial state remains unchanged.

Note:

The relay can be used as a S0-Interface according DIN 43 864.

f Out

[Hz]

0 110 w N [%]

100

0 20

110

40 80 60 100

40

20

60

80


6 Commissioning

Prior to switching on the SCHMIDT® flow sensor SS 20.600, the follow-

ing checks have to be carried out:

Mechanical installation:

o Correct immersion depth and alignment of the sensor probe ac-cording to the flow direction

o Tightening of the fastening screw or spigot nut

o Installation of the pressure safety devices

For measurements in media with overpressure, check if the fastening screw is tightened properly and pressure safety devices are installed.

Connecting cable:

o Correct connection in the field (switch cabinet or similar)

o Tightness of the sensor connector and connecting cable (flat seal must be inserted correctly into the female cable connector)

o Tight fit of the spigot nut on the cable connector at the sensor housing

After switching on the operating voltage, the sensor signals initialization by switching all four LEDs sequentially to red, orange and green.

If the sensor detects a problem during initialization, it signals the problem according to Table 5. An extensive overview of errors and their causes as well as troubleshooting measures are listed in Table 9.

If the sensor is in the correct operational state, it switches to the measur-ing mode after initialization. Flow velocity indication (both LEDs and sig-nal outputs) switches for a short period to maximum and levels off at the correct measuring value after about 10 seconds, if the sensor probe al-ready has the medium temperature. Otherwise, the process will last longer until the sensor has reached the medium temperature.

!


7 Information concerning operation

Environmental condition Temperature

The SCHMIDT® flow sensor SS 20.600 monitors the temperature of

both medium and electronics. As soon as the specified operating range of the electronics (-20 ... +70 °C) is exceeded, the sensor switches off both measuring functions associated with the medium and signals the error by means of the LED bar according to Table 5. As soon as proper operational conditions are restored, the sensor resumes measuring mode.

Even when exceeding or underrunning the operating tempera-tures for a short time, the sensor may be damaged irreversibly.

Environmental conditions Medium

The SCHMIDT® flow sensor SS 20.600 is also suitable for relatively

impure gases as long as there are no damaging, chemical aggressive constituents

20. Dust or non-abrasive particles can be tolerated as long as

they do not form any deposits on the sensor chip.

Deposits or other soiling must be detected during regular inspections and removed during cleaning because they can lead to distortion of the measurement result (see chapter 8 Service information).

Dirt or other deposits on the sensor head cause false meas-urement results.

Therefore, the sensor must be checked for contamination at regular intervals and cleaned if necessary.

Condensing liquid fractions in the medium to be measured or immersion of the sensor into liquids must be avoided at all costs.

Always avoid liquids on the sensor during operation.

It leads to serious measurement distortions and can damage the sensor in the long term.

When using the sensor outdoors, it must be protected against direct exposure to the weather.

20

Strong mineral acids e.g. can be critical; in general the suitability has to be checked.

!

!

!

!


8 Service information

Maintenance

Heavy soiling of the sensor head may lead to distortion of the measured value. Therefore, the sensor head must be checked for contamination at regular intervals. If contaminations are visible, the sensor can be cleaned as described below.

Cleaning of the sensor head

If the sensor head is soiled or dusty, it must be cleaned carefully by means of compressed air.

The sensor head is a sensitive measuring system.

During manual cleaning proceed with great care.

In case of persistent deposits, the sensor chip as well as the interior of the chamber head can be cleaned carefully by using residue-free drying alcohol (e.g. isopropyl alcohol) or soapy water with special cotton swabs.

Figure 8-1 Suitable cotton swabs with small cleaning pads

For this purpose cotton swabs that have small, soft cotton pads are suit-able, e.g. type "SP4"of the brand "CONSTIX Swabs" of the manufacturer "CONTEC". The flat, narrow side of the pads fit just between chamber head wall and sensor chip and therefore exerts a controlled, minimal pressure on the chip. Conventional cotton swabs are too big and there-fore can break the chip.

!


Under no circumstances do attempt to pressurize the chip with greater force (e.g. by swabs with thick head or lever movements with its stick).

Mechanical overloading of the sensor element can lead to irre-versible damage.

The sticks must be moved only with great care parallel to the chip sur-face back - and – forth to rub off the pollution. If necessary, several cot-ton swabs have to be used.

Before putting it into operation again, wait until the sensor head is com-pletely dried. The drying process can be accelerated by gently blowing

If this procedure does not help, the sensor must be sent to SCHMIDT Technology for cleaning or repair.

Eliminating malfunctions

The following Table 9 lists possible errors (error images). A description of the way to detect errors is given. Furthermore, possible causes and measures to be taken to eliminate errors are listed.

Causes of any error signaling have to be eliminated imme-diately. Significant exceeding or falling below the permitted operating parameters can result in permanent damage to the sensor.

Error image Possible causes Troubleshooting

Problems with the supply voltage UB: No UB present UB has wrong polarity UB < 15 V Sensor defective

Is the plug-in connector screwed on correctly?

Is the supply voltage con-nected to the control?

Is there voltage at the sensor plug (cable break)?

Is the power supply unit large enough?

No LED is lit All signal outputs at zero

Start sequence is repeated continuously (all LEDs red - yellow - green)

UB unstable: Power supply unit unable

to supply the switch-on current

Other consumers overload UB

Cable resistance is too high

Is the supply voltage at the sensor stable?

Is the power supply unit large enough?

Are the voltage losses over cable negligible?

!

!


Error image Possible causes Troubleshooting

Sensor element defective Return the sensor for repair

Supply voltage too low Increase supply voltage

Supply voltage too high Reduce supply voltage

Electronic temperature too low

Increase operating tempera-ture of the environment

Electronic temperature too high

Lower operating temperature of the environment

Medium temperature too low

Increase medium tempera-ture

Medium temperature too high

Lower medium temperature

Low signal wN is too large / small

Measuring range too small / large I-mode instead of U-mode or vice versa Medium to be measured does not correspond to ad-justment medium Sensor element soiled

Check sensor configuration Check type or measuring resistance Is foreign gas correction considered? Clean sensor head

Flow signal wN is fluctuating UB unstable Mounting conditions: Sensor head is not in the

optimum position Inlet or outlet is too short Strong fluctuations of pres-sure or temperature

Check the voltage supply Check mounting conditions Check operating parameters

Analog signal voltage per-manently at max.

Load resistance of signal output connected to +UB

Connect measuring re-sistance to AGND

Analog signal voltage per-manently at zero

Error signaling Short circuit against (A)GND

Eliminate errors Eliminate short circuit

Table 9

Transport / Shipment of the sensor

Before transport or shipment of the sensor, the delivered protective cap must be placed onto the sensor head. Avoid contaminations or mechani-cal stress.


Calibration

If the customer has made no other provisions, we recommend repeating the calibration at a 12-month interval. To do so, the sensor must be sent in to the manufacturer.

Spare parts or repair

No spare parts are available, since a repair is only possible at the manu-facturer's facilities. In case of defects, the sensors must be sent in to the supplier for repair.

A completed declaration of decontamination must be attached.

The “Declaration of decontamination” form is attached to the sensor and can also be downloaded from

www.schmidttechnology.com

under “Downloads” in “Service returns”.

If the sensor is used in systems important for operation, we recommend you to keep a replacement sensor in stock.

Test certificates and material certificates

Every new sensor is accompanied by a certificate of compliance accord-ing to EN10204-2.1. Material certificates are not available.

Upon request, we shall prepare, at a charge, a factory calibration certifi-cate, traceable to national standards.



9 Dimensions

Compact sensor

Figure 9-1

Remote sensor including wall mounting bracket

Figure 9-2


10 Technical data

Measurement-specific data

Measuring values Standard velocity wN based on standard conditions of 20 °C and 1,013.25 hPa Temperature of medium TM

Medium to be measured Standard: Air or nitrogen Optional: natural gas, biogas, CO2 and special gases

or gas mixtures

Measuring range wN Standard: 0 ... 10 / 20 / 60 / 90 / 140 / 220 m/s Special: 10 … 220 m/s in steps of 0.1 m/s

Lower detection limit wN 0.2 m/s

Measuring range TM Standard / O2 version: - 20 ... + 120 °C ATEX version: - 40 ... + 120 °C

Measuring accuracy

Standard wN ± 3 % of measured value + (0.4 % of final value; min. 0.08 m/s)

21

High precision wN ± 1 % of measured value + (0.4 % of final value; min. 0.08 m/s)

21

(only for air, nitrogen, oxygen)

Reproducibility wN ± 1 % of measured value

Response time (t90) wN 1 s (jump from 0 to 5 m/s in air)

Temperature gradient wN < 8 K/min for wN = 5 m/s

Recovery time constant < 10 s at temperature jump Δϑ = 40K @ wN = 5m/s

Measuring accuracy TM ± 1 K (10 ... 30 °C); ± 2 K remaining measuring range @ wN > 5 m/s

Operating temperature

Sensor Standard: - 20 … + 120 °C Oxygen-version: - 20 … + 60 °C ATEX-version: - 40 ... + 120 °C

Electronics - 20 … + 70 °C

Storage temperature - 20 … + 85 °C

Material

Housing Anodized aluminum

Sensor tube Stainless steel 1.4571

Through-bolt joint Stainless steel 1.4571, NBR (or FKM)

Sensor head Platinum element (glass passivated), PPO / PA

Sensor cable (remote sensor) Sheathing TPE, halogen-free

21

Under reference conditions


General data

Humidity range 0 … 95 % rel. humidity, non-condensing

Operating pressure (max.) Standard version: 16 bar Oxygen version: 20 bar Optional version: 40 bar

Display 4 x dual LEDs (green /red / orange)

Supply voltage 24 VDC ± 20 %

Current consumption Approx. 80 mA (without pulse outputs); max. 200 mA22

Analog outputs

- Type: Auto U / I

Switching Auto-U/I - Voltage output - Current output - Switching hysteresis

Maximum load capacitance

Flow velocity, temperature of medium

Automatic switching signal mode based on load resistance RL

0 … 10 V for RL ≥ 550 Ω 4 … 20 mA for RL ≤ 500 Ω 50 Ω

10 nF

Pulse outputs - Signaling:

- Pulse output 1:

- Pulse output 2:

f ~ wN: 0 m/s … wN,max → 0 Hz … fmax Standard: fmax = 100 Hz Option : fmax = 10 … 99 Hz Quantity: 1 pulse / 1 m³ | 1 pulse / 0.1 m³ | 1 pulse / 0.01 m³ (max. 100 Hz)

High-side driver connected to supply voltage (without galvanic separation) High level: > supply voltage - 3 V Short circuit current limitation: 100 mA Leakage current: IOff < 10 µA

Semiconductor relay (output galvanically separated) max. 30 VDC / 21 VAC,eff / 50 mA

Connection Plug-in connector M 12, 8-pin, male, screwed

Maximum cable length Voltage signal: 15 m, current signal / pulse: 100 m

Installation position As desired (for vertical downdraft flow: lower range limit 2 m/s at 16 bar)

Mounting tolerance ± 3° relative to flow direction

Minimum immersion depth DN 25

Type of protection IP 66 (housing), IP 67 (sensor probe)

Protection class III (SELV) or PELV (EN 50178)

ATEX category II 3G Ex nA IIC T4 Gc

Probe length

- Compact sensor

- Remote sensor

Standard: 120 / 250 / 400 / 600 mm Special: 120 ... 1,000 mm

Probe: 120 / 250 / 400 / 600 mm Cable: 10 m (in steps of 10 cm)

Weight Approx. 500 g max. (without connecting cable)

22

Without signal current of pulse output 2 (relay)


11 Declaration of Conformity


SCHMIDT Technology GmbH Feldbergstraße 1 78112 St. Georgen Germany

Phone +49 (0)7724 / 899-0 Fax +49 (0)7724 / 899-101 Email [email protected] URL www.schmidt-sensors.com

schmidt flow sensor instructions for use · symbols used in this manual ... figure 3-2 arrangement...

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